In a patent document 1 and so on, there is known a hemming processing performed by a roller-shaped hemming processing tool held by a robot arm, in addition to a conventional press-type hemming processing by upper and lower dies. On the premise of the press-type hemming processing, there have been proposed hemming processing systems in which tooling change operation of upper and lower dies according to the change of the kind of the workpiece is effectively performed, and which are suitable for high-variety low-volume manufacturing (low volume production of a wide variety of products), in patent documents 2 and 3. Similarly, on the premise of the above-described roller hemming processing, there has been proposed a hemming processing system in which the tolling change operation of the lower die according to the change of the kind of the workpiece is effectively performed, and which is suitable for the high-variety low-volume manufacturing, in a patent document 4.
In the systems described in the patent documents 2 and 3, a set of the upper and lower dies are changed by using truck (carriage) type and other conveying apparatuses, between a press machine and a storage area in which the sets of the upper and lower dies according to the kind of the workpiece are stored.
Moreover, in the system described in the patent document 4, a mounting table for the lower die is prepared near the processing stage. Furthermore, a plurality of sets in which each of lower dies that are different in accordance with the kind of the workpiece is mounted on a common general-purpose jig irrespective of the kinds (types) of the workpiece are prepared, and these are stored on the mounting table for the lower die. Then, when the kind of the workpiece are changed, the lower die and also the general-purpose jig are changed between the processing stage and the mounting table for the lower die by using forklift and so on.
However, in the conventional processing systems described in the patent documents 2 and 3, it is necessary to store a plurality of kinds of upper and lower dies having weights from several tons to several dozen tons in the horizontal manner in a storage area. Accordingly, the occupied area of the storage area necessarily becomes large, so that the space efficiency is deteriorated. Moreover, since the set of the upper and lower dies having the weight from several tons to several dozen tons is changed, the operation of the die change is complicated, the time necessary for the die change is necessarily lengthened, and an actual operation availability (availability factor) of the press machine is deteriorated. Therefore, it is not preferable.
Moreover, in the conventional processing system described in the patent document 4, the change operation of the lower die mounted on the general-purpose jig is performed by the forklift and so on. Accordingly, the change operation of the lower die requires time due to the operation of handling the heavy member, though not to the extent of the time necessary for the change of the set of the upper and lower dies. Therefore, it is not efficient. Moreover, there is a restriction of the number of the lower dies which are stored in the mounting table for the lower die. Accordingly, it is not possible to respond to the high-variety low-volume manufacturing in which the kinds of the workpiece that is the processed object are further increased. For example, in a case where it responds to the respective hemming processings of a front door and a rear door of a plurality of types of the vehicle, like the hemming processing of the door of the vehicle, the number of the lower dies to be stored is necessarily increased. Moreover, the identification of the type of the lower die to be selected and the position of the lower die within the mounting table for the lower die depend on the operator. It is not possible to flexibly respond to the change operation of the lower dies to be frequently performed. Moreover, it needs the larger space for storing the many lower dies each of which has a weight from a few hundred kilograms to several tons, as the kinds of the prepared lower dies are increased. The space efficiency is deteriorated due to the increase of the occupied area for storing the lower dies.